In recent years, with the multimediatization of information in cellular mobile communication systems as represented by mobile phones for example, transmitting large capacity data such as still images and movies in addition to speech data becomes popular in recent years. To realize the transmission of high capacity data, a technology in which a high-frequency radio band is used to obtain a high transmission rate is studied actively.
However, when a high-frequency radio band is used, although a high transmission rate can be expected in a short distance, attenuation due to transmission distance becomes greater as the distance increases. Accordingly, when the mobile communication system employing a high-frequency radio band is actually operated, the coverage area of each radio communication base station apparatuses (hereinafter “base station”) becomes small, which thus requires that a larger number of base stations be set up. Since the set-up of base stations involves large costs, a technology is strongly demanded for realizing communication services which employ a high-frequency radio band and preventing an increase in the number of base stations.
To address this demand, various relay technologies are investigated in which radio communication relay station apparatuses (hereinafter “relay stations”) are set up between a radio communication mobile station apparatus (hereinafter “mobile station”) and a base station, and communication between the mobile station and the base station is carried out via these relay stations.
Moreover, as one of relay technologies, communication between a base station and a mobile station is carried out via a plurality of relay stations simultaneously. The technology enables to obtain diversity effect by performing relay transmission in cooperation of a plurality of relay stations and by receiving signals from a plurality of relay stations by a base station and a mobile station of signal receiving side.
Moreover, a relay technology is disclosed that, to prevent propagation of errors in relay-transmission, the relay station detects errors in a relay signal and does not relay the signals having errors (see non-patent document 1).
Non-patent Document 1: “Cooperative Relaying Technique with Space Time Block Code for Multihop Communications among Single Antenna Terminals,” technical report of IEICE, The Institute of Electronics, Information and Communication Engineers, March 2004, A•P2003-342, RCS2003-365, pp. 71 to 76